The English Reformation had been going along quite nicely since the Henrician reforms had begun. Henry's only son, Edward VI, had not come of age upon his father's death, and so the country was now ruled by Protector Somerset, a man who seemed keen to advance what Henry had begun (although, it must be noted, not with such passionate zeal that he neglected the secular interests of his country).
However, not all were happy with the "progress" - religious conservatives abounded among both the clergy and the laity, and the counties of Cornwall and Devon were to pose the government a rather unique problem. Because of the counties involved in this rebellion, it is often referred to as The Western Rebellion.
The people of Cornwall did not consider themselves strictly "English" - certainly, they were attached to the island physically, but language seperated them from it spiritually. In Cornwall, the vernacular was still Cornish - a language similar to Breton. They did not appreciate the interference of the government in any matter, and when it came in the form of a drastic change to their religious practices, they would go to great lengths to defend themselves.
Archdeacon William Body ("an unscrupulous and avaricious careerist", according to historian Anthony Fletcher) was the government agent in charge of overseeing religous change in Cornwall. He visited Cornwall in 1547 to oversee inventory taking related to the dissolution of the chantries, and was attacked. When he returned there next year to ensure that images were being destroyed in line with Protestant doctrine, he was killed by a mob.
The government did not respond harshly to these events - indeed, it was characteristic of Protector Somerset that he always tried to deal leniently with the commons. This attitude can in part be blamed for both the Prayer Book Rebellion and Ket's Rebellion, as it was by his contemporary and adviser, William Paget:
"Marry, the King's subjects out of all discipline, out of obedience, caring neither for Protector or King, and much less for any other mean officer. And what is the cause? Your own levity, your softness, your opinion to be good to the poor."
The Prayer Book Rebellion
Cornish opposition to the Edwardian reforms turned into full-scale rebellion when it was revealed that the new Prayer Book to be used throughout the Church of England was to be in English, not Latin. This was another basic Protestant tenet - Catholics believed services should be in Latin, as they signified communication between the priest and God without any other individual being involved. Protestants wanted the services read in English, which opened up the word of God to all the laity (in fact, many of the clergy had no comprehension of the word of God, being unable to read Latin and having merely learnt their services by rote!)
It seems the Cornish commons wanted services to be read in Latin or Cornish, which provoked Bishop Cranmer's comment that surely more Cornishmen understood English than Latin. There were also some clear misunderstandings on the parts of the rebels - they believed that the new Prayer Book ruled that they could only baptise their children on sundays.
The rebels gathered at Crediton on June 20th, 1549. At first, the Protector did not view the rebellion as serious, and he had more pressing matters on his mind - troops were commited in Scotland and a French invasion of Boulogne (currently in English hands) seemed imminent. He was also facing enclosure riots around the country. The rebels laid siege to Exeter after issuing their demands.
The demands of the rebels
The demands of the rebels were mainly religious in their nature, and they wished a return to the Catholicism of old. They called for the restoration of the Six Articles (which had enforced six fundamental tenets of Catholic belief), and a halt on any religious reforms carried out under a Protector. The demands had been drawn up by a small group of priests who formed the core of the rebellion, and hence it is hardly surprising they were mainly religious in nature.
There were also social element to the rebels demands - they called for a restriction on the number of servants the gentry could keep, and the confisfaction of ex-monastic lands from the gentry and their redistribution. Although these demands look entirely secular on the service, it should be noted that the gentry had benefitted the most from the English Reformation. By attacking their position and their vested interest in the continuation of the Reformation, the rebels attacked the Reformation itself.
The end of the rebels
Of course, the rebels could not pose a serious military threat to the government. At first the Protector had offered them a free pardon in the hope they would disperse peacefully, but when they did not he sent a force of troops to lift the siege of Exeter and the rebel army was eventually destroyed in a battle at Okehampton in mid-August. The Western Rebellion had achieved little, and had never looked as dangerous as Ket's Rebellion. However, the Protector saw danger as imminent because war with France had broken out on August 8th, and it was feared the French could encourage the rebellion (in fact, the rebels had never communicated with the French.)